Summary
God’s banquet table has plenty of seats waiting to be filled. It is our duty to invite people to join us at the banquet—not that we can force them to come, but we do still need to give them the invitation. All are invited to the feast, even sinners. Although since few choose to respond, few are chosen (cf. Matthew 22:14).
Content
Just as Paul received grace (Romans 1:5), he urges others to submit to God, so that they too may belong to Jesus Christ as he does.
Because all humans are called by God (even if not all respond = choose God, thus becoming chosen in turn), it is true to say that we also, like Paul, ought to “call all the Gentiles to obedience” (Romans 1:5—note that it is all the Gentiles, not just some groups of elect Gentiles). Even if we are already “among those… who are called to belong to Jesus Christ” (Romans 1:6), those “loved by God and called to be His holy people” (Romans 1:7), well, God wishes to fill His table for the wedding banquet (cf. Matthew 22:8-14), so we are to invite all we meet, calling them to join us.
For it is not just people who already believe that need to be told of and reminded about Jesus. It is everybody, sinners included. When we call them to obedience, it isn’t an exhortation to follow some set of legalistic rules, but an exhortation to submit to God by believing in Jesus Christ, that they too might come to belong to Him. For “it is not the healthy who need a doctor, but the sick” (Matthew 9:12), since Jesus “did not come to call the righteous, but sinners” (Matthew 9:13). And if that is Jesus’ attitude towards sinners, then we too most certainly also need to desire their repentance and salvation.
It is of course important to note that in broad strokes we are the sinners in view too, not just “them” (whoever exactly “them” may be).